The effects of histamine sensitizing factor (HSF) on vascular permeability will be studied further, especially in relation to the development of experimental allergic encephalomyelitis (EAE) in Lewis rats. The presence of leukocytes and immunoglobulins in the central nervous system of rats afflicted with EAE will be studied. Further studies will be conducted with HSF on mouse lymphocytes to determine if it acts by blocking beta-adrenergic receptors.